<template>
  <div>
    <span v-if="flag === null" class="undo">0: 未完成</span>
    <span v-if="flag === false" class="error">0: 错误</span>
    <span v-if="flag" class="right">0: 正确</span>
  </div>
</template>

<script>
export default {
  name: 'Flag',
  props: {
    flag: {
      type: Boolean
    }
  }
};
</script>

<style scoped>
.right {
  color: green;
}
.error {
  color: red;
}
.undo {
  color: #ccc;
}
</style>